Gyromagnetic circuit element

ABSTRACT

1. A circuit element, comprising, a tubular ferrite body having a length greater than its circumference, a conductive member encircling said body, said member being electrically insulated from all other conductive members, and means for applying a unidirectional magnetic field to said body.

United States Patent [191 Zaleski Oct. 29, 1974 [54] GYROMAGNETIC CIRCUIT ELEMENT 2,824,288 2/1958 Sensiper 333/24 G 1 mm John Zaleski, Valhalla, 3:333:33? 211323 5332221113.......:::::::::::::::: 333%; i [73] Assignee: The Singer Company, New York, OTHER PUBLICATIONS N.Y. Radio & Television News, Radio-Electronic Engineer- [221 1958 ing edition, pp. 11-13, 24, November, 1951, 343'7ss. [21] Appl. No.: 716,816

Primary ExaminerMaynard R. Wilbur Assistant Examiner-Richard E. Berger 52 US. Cl 333 24.1 332 51 W, 343 18 D, 1 I 43/787, 313/913 Attorney, Agent, or Firm-T. W. Kennedy [51] Int. Cl. H0lp l/32 [58] Field of Search 333/24 G, 24.1, 24.2, 24.3; EXEMPLARY CLAIM 332/51 51 w; 336/172 553 3 1. A circuit element, comprising, a tubular ferrite 7 body having a length greater than its circumference, a conductive member encircling said body, said member [56] References being electrically insulated from all other conductive UNlTED STATES PATENTS members, and means for applying a unidirectional 2,748,386 5/.1956 Polygoroff 343/787 magnetic field to said body. 2,820,200 111958 Dupre..... 333 24 0 x 2,823,382 2/1958 Blok 343/787 x 13 Claims, 5 Drawmg Figures GYROMAGNETIC CIRCUIT ELEMENT This invention relates to an improved gyromagnetic circuit element particularly suitable for use with microwave energy.

It is well known that certain polyirons and ferrites, when subjected to a suitable magnetic field, are capable of altering incident microwave energy by rotating its plane of polarization, shifting its phase or absorbing it. The class of materials exhibiting these properties has come to be known in the art as gyromagnetic ferrites," and the term ferrite" whenever used in the present application is intended to refer to any of those substances having the above mentioned capabilities.

Practical devices embodying ferrites frequently employ an elongated rod or tube of ferrite placed within the microwave field to be altered and biased by a steady magnetic field. Various useful devices have been constructed, such as attenuators, power dividers, duplexers, isolators, modulators, etc., by utilizing one or more of the properties of phase shift, polarization rotation, or absorption. The present invention is applicable to all of these devices and comprises an improved ferrite circuit element in which the properties of phase shift, polarization rotation and absorption are greatly enhanced.

An object of the present invention is to improve the performance of ferrite microwave circuit elements.

Another object is to provide a ferrite circuit element exhibiting increased phase shift, polarization rotation and absorption properties.

Briefly stated, one embodiment of the invention comprises a cylindrical tube of ferrite around which is wound a single layer of insulated wire. The ends are left unconnected. In another embodiment, a number of bands of conductive material are deposited directly on the ferrite tube, each band completely encircling the tube. Either embodiment, when replacing an element without conductors and with or without a dielectric coating, yields vastly improved results.

For a clearer understanding of the invention reference may be made to the following detailed description and the accompanying drawing in which:

FIG. I is an elevation view of a preferred embodiment of the invention;

FIG 2 is an end view of the device of FIG. 1 with the wire removed;

FIG. 3 is a schematic diagram of a system employing the invention as one component;

FIG. 4 is an elevation view of another embodiment of the invention; and

FIG. 5 is a view, partly in elevation and partly in section, of yet another embodiment of the invention.

Referring first to FIG. I, there is shown a body 11 of ferrite around which is a closely wound single layer coil of insulated wire. As clearly shown in FIG. 2, the body 11 is cylindrical in form and has an axial aperture extending throughout its length. The ends 13 and 14 of the coil are not connected either to each other or to anything else but are left unconnected. It has been found that a transducer such as shown in FIG. 1 may be directly substituted for a similar transducer without the coil with greatly improved results. For example, the transducer of FIG. 1 is found to be an excellent microwave modulator and may be used in the system shown in FIG. 3.

Referring now to FIG. 3, there is shown a system for modulating microwave energy. This system is more 2 fully described in the copending application of John F. Zaleski, Ser. No. 683,91 1 filed Sept. 13,1957 for Modulating System, now abandoned, and will be but briefly described herein. Microwave energy from a source 16 passes through a duplexer 17 to an antenna 18 which radiates a beam of microwave energy to a transducer 19. The transducer 19 includes a ferrite body and may be like that shown in any of FIGS. 1, 4 and 5 of the present application or may be similar to the transducers described in the aforementioned copending application, Ser. No. 683,911. In any event, the ferrite body is magnetically biased by some means, shown in FIG. 3 for example as comprising two hollow cylindrical permanent magnets 2 l and 22 affixed to the ends of the ferrite body and arranged with like poles facing each other. A conductor 23 carrying a signal current is placed near the transducer 19 so that the magnetic field of the conductor 23 may traverse the surface of, or enter, the ferrite. The microwave energy from antenna 18 is modulated by the current in conductor 23 and reradiated to the antenna 18 and after passing through the duplexer 17 is picked up by the receiver 24 where the signal is recovered.

Using the system of FIG. 3 with a microwave source of 8,800 mcps, the transducer of FIG. 1 was compared with a transducer identical in all respects except that the coil 12 was omitted. In both cases, the ferrite body was a tube 3 inches long with an outside diameter of one-fourth inches and an inside diameter of one-eighth inches, made of a commercial ferrite known as Ferramic R-l, a magnesium oxide, manganese oxide, ferric oxide composition, obtainable from the General Ceramics Corporation of Keasbey, NJ. The coil comprises a closely wound single layer of No. 40 wire covered with low loss insulation 0.0005 inches thick having a dielectric constant of approximately 2. Biasing magnets one-fourth inches long with an outside diameter of one-fourth inches and an inside diameter of one-eighth inches were affixed to the ends of the ferrite tube. A direct comparison of the effects of the two transducers showed that the signal recovered by the receiver 24 was approximately 20db stronger when using the transducer with the coil than when using the same arrangement without the coil.

Another test employed the device of FIG. 1 as above described except that the ends 13 and 14 were connected together. This arrangement showed a vast improvement over the bare ferrite, but less improvement than when the ends were unconnected.

The reasons for the improvement observed are not fully understood but it is believed that the presence of the conductor around the ferrite tube aids in concentrating the microwave energy upon the surface of or within the ferrite. It has previously been shown (see the copending application of John F. Zaleski, Ser. No.

. 581,640 filed Apr. 30, I956, for Microwave Polarization Rotator, now abandoned) that a dielectric layer of proper thickness and dielectric constant surrounding a ferrite rod improves its polarization rotation capabilities and it might be thought at first that the dielectric around the wire of the coil 12 was responsible for the improvement observed. While the dielectric undoubtedly contributes to the improvement it is not the sole cause because improvement is observed without any dielectric.

Referring now to FIG. 4 there is shown a hollow cylindrical tube 26 of ferrite upon which are a plurality of conductive bands 27 each of which completely encircle the tube 26 and which are spaced from each other as shown. Although the improvement obtained with this device is not as great as with that of FIG. 1, the improvement is greatcompared to a bare ferrite tube. in the drawing the thickness of the bands 27 have been greatly exaggerated, as in reality they are very thin. For example, a device according to FIG. 4 was constructed by evaporating silver on a ferrite tube, plating copper over the silver and cutting away both surfaces to form the spaces between the bands. The tube was 3 inches long, one-fourth inches in outside diameter and one-eighth inches in inside diameter. The conductive bands were approximately 0.010 inches wide, 0.002 inches thick and spaced apart by approximately 0.005 inches. When this device was tested in the system shown in FIG. 3 (including the magnets 21 and 22) the signal recovered by the receiver 24 was found to be approximately ldb greater than when using a similar tube of bare ferrite.

It is possible to obtain results even better than that obtained with the device of FIG. '1 by properly combining a conductor around the ferrite tube with a dielectric sheath. In FIG. there is shown a ferrite tube 31, which may be identical to that employed in the other embodimerits, around which is wound a helix 32 of bare wire. An annular magnet is afiixed to each end of the tube, one of which is shown at 33. A dielectric tube 34 surrounds the entire structure and is held in position by two dielectic washers, one of which is shown at 35, which may, for example, be made of foam polystyrene. One device constructed in accordance with FIG. 5 employed a tube of ferrite 3 inches by one-fourth inches by one-eighth inches and the coil was wound with No. 40 bare wire with the turns spaced apart by approximately 0.003 inches. The dielectric tube 34 was made of polystyrene having a dielectric constant of about 1.6, having an outside diameter of 0.5 inches, and a wall thickness of 0.0l0 inches. When tested in the system of FIG. 3, the signal recovered by the receiver 24 was greater than with any other transducer so far tested.

Although the transducer of the invention has been described in connection with a particular microwave modulator, it will be understood that it has wide application. For example, consider the well known gyromagnetic ferritev waveguide modulator which is the basic element of many devices such as duplexers, power dividers, isolators, attenuators, etc. Such a modulator comprises a ferrite body within a waveguide and has a low frequency or a unidirectional magnetic field coupled to the waveguide. It has been found that the addition of a helical winding, such as that shown in FIG. I, greatly improves the operation. As another example, the transducer of the present invention may be used in a microwave modulator similar to that shown in FIG. 3 wherein the signal carrying conductor passes through the aperture in the ferrite tube. Many other applications of the invention will occur to those skilled in the What is claimed is:

l. A circuit element, comprising, a tubular ferrite body having a length greater than its circumference, a conductive member encircling said body, said member being electrically insulated from all other conductive members, and means for applying a unidirectional magnetic field to said body.

2. A circuit component, comprising, a tubular ferrite body, a plurality of annular conductors around the periphery of said body, said conductors being electrically insulated from all other conductive members, and means for applying a unidirectional magnetic field to said body.

3. A gyromagnetic transducer comprising a tubular ferrite body, a plurality of conductive turns around said body, said conductive turns being spaced from each other and electrically insulated from all other conductive bodies, and means for magnetically biasing said body.

4. A microwave circuit component comprising a cylindrical body of ferrite with a length greater than its circumference and having an axial aperture therethrough, a conductive member encircling said body, said member being electrically insulated from all other conductive members, and means for applying a steady magnetic bias to said body.

5. A transducer comprising a tubular body of ferrite and conductor means circumjacent the periphery of said body of ferrite and distributed along the length thereof as a plurality of bandlike portions with the bandlike portions spaced longitudinally with respect to each other.

6. A microwave circuit component comprising a tubular ferrite body, a multiturn helical conductor around said body, adjacent turns of said helical conductor being insulated from each other, said conductor being electrically insulated from all other conductors, and means independent of said conductor for applying a steady magnetic field to said body.

7. A microwave circuit component comprising a cylindrical body of ferrite having an axial aperture therethrough, and a multiturn helical conductor around the periphery of said body, adjaceht turns of said helical conductor being insulated from each other, opposite ends of said conductor being insulated from each other, all of said conductor being insulated from all conduc' tive bodies other than itself, and two permanent magnets, one abutting each end of said body, for providing a magnetic bias for said body.

8. An electrical circuit component comprising, a tubular ferrite body, a single layer winding of insulated wire around said body, said wire being electrically insulated from all other conductors, and means for applying a steady magnetic field having an axial component to said body.

9. A circuit component comprising a tubular ferrite body and a plurality of annular conductive elements upon the periphery of said body, said annular elements being axially spaced from each other.

10. A circuit component comprising a tubular ferrite body and a plurality of annular conductive elements upon the periphery of said body, said annular elements being spaced from all other conductive bodies and axially spaced from each other.

11. A circuit component comprising, a tubular ferrite body, a multiturn coil of conductive wire around said body, said coil being electrically insulated from all other conductors, a dielectric tube coaxial with and encircling said tubular ferrite body, and means for applying a steady magnetic bias to said body.

12. A circuit component comprising, a tubular ferrite body, a single layer multiturn coil of conductive wire around said body, said coil being electrically insulated from all other conductors, the ends of said coil being axially spaced from each other, said coil being electrically insulated from all other conductors, the ends of said coil being insulated from each other, two permanent magnets, one abutting each end of said body, for

5 providing a magnetic bias, and a dielectric tube coaxial with, radially spaced from and encircling said ferrite tube, said magnets and said coil.

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1. A circuit element, comprising, a tubular ferrite body having a length greater than its circumference, a conductive member encircling said body, said member being electrically insulated from all other conductive members, and means for applying a unidirectional magnetic field to said body.
 2. A circuit component, comprising, a tubular ferrite body, a plurality of annular conductors around the periphery of said body, said conductors being electrically insulated from all other conductive members, and means for applying a unidirectional magnetic field to said body.
 3. A gyromagnetic transducer comprising a tubular ferrite body, a plurality of conductive turns around said body, said conductive turns being spaced from each other and electrically insulated from all other conductive bodies, and means for magneticAlly biasing said body.
 4. A microwave circuit component comprising a cylindrical body of ferrite with a length greater than its circumference and having an axial aperture therethrough, a conductive member encircling said body, said member being electrically insulated from all other conductive members, and means for applying a steady magnetic bias to said body.
 5. A transducer comprising a tubular body of ferrite and conductor means circumjacent the periphery of said body of ferrite and distributed along the length thereof as a plurality of bandlike portions with the bandlike portions spaced longitudinally with respect to each other.
 6. A microwave circuit component comprising a tubular ferrite body, a multiturn helical conductor around said body, adjacent turns of said helical conductor being insulated from each other, said conductor being electrically insulated from all other conductors, and means independent of said conductor for applying a steady magnetic field to said body.
 7. A microwave circuit component comprising a cylindrical body of ferrite having an axial aperture therethrough, and a multiturn helical conductor around the periphery of said body, adjacent turns of said helical conductor being insulated from each other, opposite ends of said conductor being insulated from each other, all of said conductor being insulated from all conductive bodies other than itself, and two permanent magnets, one abutting each end of said body, for providing a magnetic bias for said body.
 8. An electrical circuit component comprising, a tubular ferrite body, a single layer winding of insulated wire around said body, said wire being electrically insulated from all other conductors, and means for applying a steady magnetic field having an axial component to said body.
 9. A circuit component comprising a tubular ferrite body and a plurality of annular conductive elements upon the periphery of said body, said annular elements being axially spaced from each other.
 10. A circuit component comprising a tubular ferrite body and a plurality of annular conductive elements upon the periphery of said body, said annular elements being spaced from all other conductive bodies and axially spaced from each other.
 11. A circuit component comprising, a tubular ferrite body, a multiturn coil of conductive wire around said body, said coil being electrically insulated from all other conductors, a dielectric tube coaxial with and encircling said tubular ferrite body, and means for applying a steady magnetic bias to said body.
 12. A circuit component comprising, a tubular ferrite body, a single layer multiturn coil of conductive wire around said body, said coil being electrically insulated from all other conductors, the ends of said coil being electrically insulated from each other, a tubular dielectric element encircling said ferrite body and said coil, and means independent of said coil for applying a steady magnetic field having an axial component to said body.
 13. A circuit component comprising, a tubular ferrite body, a single layer multiturn coil of bare conductive wire around said body, adjacent turns of said coil being axially spaced from each other, said coil being electrically insulated from all other conductors, the ends of said coil being insulated from each other, two permanent magnets, one abutting each end of said body, for providing a magnetic bias, and a dielectric tube coaxial with, radially spaced from and encircling said ferrite tube, said magnets and said coil. 